This invention relates to a series of novel polymeric compounds and to a method for their preparation. In a more particular aspect, this invention concerns itself with novel polyaromatic esters curable by intramolecular cyclization.
Polymeric materials with cyclic structures on either the chain backbone or side groups usually have good thermal stability and high heat resistance. These factors, however, contribute to the low solubility and high melting temperature characteristics exhibited by these polymers thus making their processability a problem.
For example, it is known that polymers, such as polyphenylquinoxalines and aromatic polyether-keto-sulfones, which contain 2,2'-di(phenylethynyl) biphenyl units show increased chemical and heat stability after thermal curing. The curing process has been described as two adjacent phenylacetylenyl groups undergoing intramolecular cyclization to form 9-phenyl benzanthracene units. The intramolecular cyclization of phenylethynyl groups present in the polymer contributes considerably to its rigidity and thermal stability. However, the poor processability of such materials constitutes a problem which limits their usefulness. The present invention, therefore, was directed toward a solution to that problem and the development of easily processable novel polyaromatic esters with good stability before curing and with improved thermal and chemical resistance after curing. As a consequence, it was found that novel polyaromatic esters could be developed which possessed the requisite stability before curing and improved thermal and chemical resistance after curing in order to overcome the processability problems associated with prior art polyesters.